population genetics

[Lab news] Baumann & Therkildsen lab on a silverside road trip

28 October 2018. Members of the Therkildsen (Nina Therkildsen, Maria Akopyan) and Baumann labs (Hannes Baumann, Callie Concannon) went on a joint road trip together to sample juvenile Atlantic silversides for our NSF project about the genomic underpinnings of local adaptation in the ocean. We targeted again three sites, Morehead City NC, Oregon Inlet NC, and Chincoteague Island VA, sampling silversides via beach seine. The weather was lousy and the work strenuous, but the mood elated, because we got all the fish we needed for subsequent genomic and otolith analyses.
What a great collaboration. Check out some of the pictures from the trip below.






[Research news] A day at Harvards MCZ

Friday, 8 June 2018. Hannes and Maria traveled to Boston’s Harvard University to meet with Valentina di Santo from the Lauder Lab at the Museum for Comparative Zoology. Thanks to our collaborators there, we were able to use a 2D-digital X-ray machine there, which we needed to complete the next big step in our Menidia Gene project.

Genetic & body samples went in different vials
Maria Akopyan processing the fish after x-raying
Maria and Valentina in the shark section of the collection

A few weeks ago, Maria had already measured each individual fish's length, weight, shape, routine metabolism, and maximum sustained swim speed. The next trait we're keen on mapping quantitatively to the silverside genome is the number of vertebrae, which we know increases in wild populations from south to north. What will our South/North hybrid F2 generation show?
At the Lauder lab, ‘lunch together’ is common thing

The famous Latimeria from the collection
Thanks to Valentina's excellent help, the work went without a hitch. At the end, we even had some spare time to enjoy the great atmosphere int the Lauder Lab during lunchtime, the tour through various lab installations, the experimental fish, and even the adjacent Harvard Zoological museum. Thank you all for the fun day at Harvard!

Settings used for x-raying juvenile silversides
Hannes and Valentina in the x-ray room
George Lauder adjusting equipment in the swim lab

The 282 fish are now split in a DNA sample for extraction and a body sample for further trait measurements.


[New Publication] Species or ecotype? The curious case of the Key silverside Menidia conchorum

What constitutes a species …

…in the true sense has kept biologist’s head scratching for quite some time, and matters have only gotten more complex since the thunderous advent of genetic methods. Yet the distinction between a species and – say – an ecotype of a species is more than just academic quibble.

In the case of the key silverside, Menidia conchorum, a species that is only found in the hypersaline ponds on the Florida Keys, it’s quite literally an existential question. So far, the protocols and steps of protection apply only in cases of threatened species, which is perhaps something that ought to change.

O’Leary et al. went down to the Florida Keys and sampled the silversides in order to compare them morphologically and genetically to the ‘parent’ species, the tidewater silverside Menidia peninsulae. Their findings show that key silversides are distinct, but not quite their own species yet. In addition, the study revealed the large amount of inbreeding and genetic drift that is happening in each of these small hypersaline ponds.

The paper concludes that although ‘only’ an ecotype, the key silverside is threatened by loss of habitat and therefore still needs our protection!

O'Leary et al. BMS2016
Depiction of morphometric landmarks (upper left) and distinguishing shapes (lower left) between tidewater and key silverside (M. peninsula & M. conchorum). Key silversides are an ecotype that can only be found in hypersaline ponds on the Florida Keys (right: lead and co-authors seining).

O’Leary, S.J., Martinez, C.M., Baumann, H., Abercrombie, D.L., Poulakis, G.R., Murray, C.H., Feldheim, K.A., Chapman, D.D. (2016)
Population genetics and geometric morphometrics of the Key silverside, Menidia conchorum, a marine fish in a highly fragmented inland habitat.
Bulletin of Marine Science 92:33-50